1. Field of the Invention
The present invention relates to a gas sensor.
2. Description of Related Art
Recently, a fuel cell which is expected for a power source for a fuel cell vehicle or the like discharges hydrogen (or gas to be detected) not consumed by power generation from an anode of the fuel cell. The hydrogen is diluted with cathode off-gas (or dilution gas) flowing from a cathode of the fuel cell, and subsequently discharged to the outside of the vehicle (or outside). Then, the concentration of hydrogen in the gas discharged to the outside of the vehicle (or diluted gas) is detected by a hydrogen sensor (or gas sensor).
Accompanying the power generation, the fuel cell also generates moisture (or steam) in the cathode, which makes the cathode off-gas and the diluted gas flowing toward the hydrogen sensor become a high humidity gas. Herein, if the steam contained in the diluted gas condenses to be dew condensation water thereby being attached to a detector element of the hydrogen sensor, detection sensitivity of hydrogen becomes to be lowered.
To address the above mentioned drawback, Japanese Laid-Open Patent Publication No. 2003-294675 proposes a hydrogen sensor comprising a heater (or heating unit). Herein, the hydrogen sensor with a heater prevents the generation of the dew condensation water, and also prevents the dew condensation water from being attached to the detector element. Note the output of the heater is controlled by a temperature sensor arranged at a vicinity of the heater such that the generation and the attachment of the dew condensation water may be prevented based on a temperature of the heater detected by the temperature sensor.
However, as mentioned hereinbefore, if the temperature sensor for detecting the heater temperature is included, the number of the components of the hydrogen sensor increases, resulting in the difficulty and inconvenience for downsizing the hydrogen sensor.